Biomedical subjects
D G Payan
Publications and source records attributed to D G Payan.
Mediation of pulmonary immunity and hypersensitivity by neuropeptides.
Noxious challenges and inflammatory reactions in pulmonary tissue selectively stimulate different subsets of peptidergic nerve fibers to release distinct neuropeptides, that elicit local and systemic responses similar to those of immediate hypersensitivity. The sensory neuropeptides affect functions of leukocytes, epithelial glands, and smooth muscle cells directly through receptor-medicated processes, and indirectly, through the actions of mediators released from mast cells stimulated by the peptides. The specificity of neuropeptide recognition by pulmonary lymphocytes, smooth muscle cells, mast cells and basophils, and the functional diversity of these neuropeptides suggests that the nervous system modulates immediate and delayed hypersensitivity responses in the lung by unique mechanisms.
Receptor-mediated mitogenic effects of substance P on cultured smooth muscle cells.
The neuropeptide substance P, a known mitogen for human blood T-lymphocytes, now is shown to stimulate proliferation of embryonic rat aortic smooth muscle cells of the A7r5 line, at concentrations of 10(-9) M to 10(-6) M. Neurotensin (NT), that has vascular and smooth muscle activity similar to SP, failed to induce proliferation of A7r5 cells. At proliferation-enhancing concentrations, SP increased the concentration of cytosolic Ca2+ in A7r5 cells, suggesting activation of the phosphatidylinositol pathway. Binding of [125I]-substance P to A7r5 cells reached equilibrium rapidly at 4 degrees C, and was saturable, implying that the activation of smooth muscle cells by SP is a receptor-mediated process.
Modulation of lymphocyte function by sensory neuropeptides.
Neuropeptides present in the peripheral nervous system (PNS) and central nervous system (CNS) modify diverse functions of human, murine and guinea pig mononuclear leukocytes in vitro and in vivo by receptor-mediated mechanisms. Both stimulatory and inhibitory effects on lymphocytes and macrophages have been demonstrated for different neuropeptides in vitro at concentrations which are similar to those in the circulation and in tissues. The dissociation constant (KD) for the binding of a neuropeptide to its lymphocyte receptor is within the range of concentrations that evoke lymphocyte responses critical to immunity and hypersensitivity. The receptor-mediated interactions of diverse neuropeptides with immunocompetent cells provide one mechanism through which the PNS may influence localized immune responses and the CNS may alter systemic immunity.
Neuropeptide regulation of the expression of immediate hypersensitivity.
Peptide mediators of sensory nerves that are released in tissues by noxious chemical and physical insults and by diverse biologic challenges rapidly elicit local and systemic responses similar to those of immediate hypersensitivity. The sensory neuropeptides have direct effects on the functions of smooth muscles, blood vessels, leukocytes, and epithelial glands and indirect effects through the actions of mediators released from mast cells stimulated by the peptides. Sensory neuropeptides exhibit cellular specificity, as exemplified by the greater potency of substance P in activating mucosal mast cells than connective tissue mast cells. The capacity of somatostatin to inhibit release of mediators from basophils challenged by IgE-dependent mechanisms, but not by basic peptides or ionophores, illustrates the biochemical specificity of the neuropeptides. The selective release of distinct sensory neuropeptides from different subsets of nerve endings, the specificity of neuropeptide recognition by mast cells, basophils, and other target cells, and the diversity of direct and indirect activities of the neuropeptides suggest that sensory nerves may initiate and modulate immediate hypersensitivity by unique mechanisms.
Endogenous somatostatin-like peptides of rat basophilic leukemia cells.
The tetradecapeptide somatostatin (SOM 14) and a 28-amino acid biosynthetic precursor (SOM 28) are constituents of diverse neuroendocrine tissues that are released by noxious stimuli from a subset of sensory nerve endings, and substantially modify the functions of basophils and mast cells. SOM-like factors were detected initially in the fluid phase of suspensions of immunologically challenged rat basophilic leukemia cells (RBL), and were purified from ethanol/0.2 M acetic acid (3/1, v/v) extracts of replicate portions of 3 X 10(9) RBL. Sephadex G-25 columns resolved factors of over 10,000, 2000 to 4000, and 300 to 1200 daltons that are antigenically related to SOM 14, as assessed by a radioimmunoassay specific for SOM 14. Only the two larger factors were detected by a radioimmunoassay for SOM 28(1-14), which binds to prepro-SOM and SOM 28 but not SOM 14. Reverse-phase high performance liquid chromatography distinguished the two smaller SOM peptides of RBL from SOM 28 and SOM 14, respectively. Amino acid analyses showed major differences in composition between the 2000 to 4000 dalton SOM of RBL and SOM 28. Picomolar to nanomolar concentrations of both of the smaller SOM peptides of RBL inhibited the IgE-dependent release of histamine from basophils to the same extent as SOM 14. The finding of 3 to 5 ng of structurally unique SOM-like peptides per 10(8) RBL suggests that endogenous mechanisms analogous to those of specialized sensory neurons may regulate the expression of hypersensitivity.
Potentiation of mitogen-induced human T-lymphocyte activation by retinoic acid.
The capacity of retinoic acid to modulate human T-lymphocyte and B-lymphocyte activation by mitogens was examined. T-lymphocyte proliferation stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) or phytohemagglutinin was enhanced by 5 nM to 5 microM retinoic acid in a dose-dependent manner with a 65 +/- 35% (SD) increase (n = 6, P less than 0.01) in TPA-stimulated proliferation induced by 5 microM retinoic acid. Retinoic acid enhanced T-lymphocyte proliferation over a wide range of background proliferation induced by different TPA concentrations. Retinoic acid alone did not stimulate T-lymphocyte proliferation. In contrast retinoic acid inhibited B-lymphocyte proliferation stimulated by TPA or phytohemagglutinin with 26.7 +/- 23.4% inhibition of TPA-stimulated proliferation induced by 5 microM retinoic acid (P less than 0.02). Retinoic acid had intermediate effects on the proliferation of different mixtures of T- and B-lymphocytes stimulated by TPA or phytohemagglutinin. The recognition that retinoic acid has opposing effects on human T- and B-lymphocyte activation by mitogens may account for the conflicting reports of the effects of retinoids on the immune response of unpurified human lymphocyte preparations.
Structural diversity of the fibroblast-activating factors generated by human blood monocytes and U937 cells.
The incubation of purified human blood monocytes with phytohemagglutinin (PHA) and of cultured U937 human monocyte-like cells with phorbol myristate acetate (PMA) evoked the generation of fibroblast-activating activity, as assessed by stimulation of the uptake of [3H]thymidine by human dermal fibroblasts. Filtration of the supernates from monocytes and U937 cells on Sephadex G-75 resolved fibroblast-activating factors of m.w. 25,000 to 40,000, designated FAF-M and FAF-U937, respectively, from smaller factors of an apparent m.w. of approximately 10,000. FAF-M and FAF-U937 were acidic by isoelectric focusing with respective pI values of 4.0 to 5.2 and 5.4 to 5.6. The smaller factors from both sources filtered on Sephadex G-25 in phosphate-buffered saline with an apparent m.w. of 10,000. However, filtration of the same factors on Sephadex G-25 in 0.1 M acetic acid revealed one predominant fibroblast-activating activity for each cell source of an apparent m.w. of 500 to 1000. The 500 to 1000 dalton factors were inactivated by treatment with trypsin and subtilisin, suggesting that the activity was attributable to fibroblast-activating peptides, termed FAP-M and FAP-U937. FAP-M and FAP-U937 each appeared to be composed of a predominant hydrophilic activity by reverse-phase high-performance liquid chromatography. Human blood monocytes and U937 monocytes both produce structurally diverse fibroblast-activating proteins and peptides, which may contribute to the immunologic regulation of wound healing and fibrosis.
Inhibition by somatostatin of the proliferation of T-lymphocytes and Molt-4 lymphoblasts.
The proliferation of Molt-4 lymphoblasts and phytohemagglutinin-stimulated human T lymphocytes in vitro was inhibited significantly by 10(-12) to 10(-10) M to 10(-13) to 10(-9) M somatostatin, as assessed by the uptake of [3H]thymidine and [3H]leucine, respectively. The inhibitory effect of somatostatin was not attributable to cytotoxicity and was associated with a mean degradation of 52 and over 95% of immunoreactive somatostatin, respectively, after 3 and 24 hr of incubation at 37 degrees C. The specific suppression of Molt-4 lymphoblasts and T lymphocytes by somatostatin represents a distinct mechanism for the specific regulation of immunological responses by neuropeptides of the peripheral nervous system and gastrointestinal tract.
Immunopathogenetic roles of leukotrienes in human diseases.
The recent definition of the pathways of generation and structures of diverse products of the lipoxygenation of arachidonic acid has established the identity of a new family of mediators of hypersensitivity and inflammation. Studies of the effects of these mediators have shown that leukotrienes C, D, and E, the constitutents of the slow-reacting substance of anaphylaxis (SRS-A), are extremely potent smooth muscle contractile and vasoactive factors. Leukotriene B is a highly active stimulus of neutrophil and eosinophil functions and suppresses the immunological capabilities of T lymphocytes. The development of specific and sensitive radioimmunoassays has permitted the detection of elevated concentrations of leukotrienes in tissues or exudates in several diseases, including asthma, diverse allergic states, adult respiratory distress syndrome, psoriasis, spondyloarthritis, and gout. The application of selective inhibitors and antagonists of leukotrienes will clarify their pathogenetic contributions in human diseases and may yield new therapeutic approaches.
Changes in immunoregulatory lymphocyte populations in patients with histoplasmosis.
Circulating T-lymphocyte subpopulations were enumerated in 65 patients with histoplasmosis and correlated with the different clinical manifestations of the disease. Acute pulmonary histoplasmosis, rheumatologic, disseminated, and chronic inflammatory manifestations of histoplasmosis were all associated with a significant elevation above normal of OKT8+ (suppressor-cytotoxic) lymphocytes and a significantly lower than normal OKT4+ (helper-inducer)-lymphocyte to OKT8+-lymphocyte ratio. In contrast, cavitary disease was associated with an increase in OKT4+ lymphocytes, a decrease in OKT8+ lymphocytes, and a higher than normal OKT4/OKT8 ratio. Clinical recovery was associated with normalization of these values. Functional activity determined by coculture techniques correlated closely with T-lymphocyte subset measurements. These distinct subset abnormalities may help monitor immunological aspects of disease activity.
Indomethacin enhances the proliferation of mitogen-stimulated T lymphocytes of homosexual males with persistent generalized lymphadenopathy.
The possibility that cyclooxygenase products of arachidonic acid might contribute to the defective T lymphocyte function of homosexual men with the reactive lymph node syndrome was examined in vitro. T lymphocyte proliferation, assessed by the uptake of [3H]thymidine after the addition of phytohemagglutin, was 72,870 +/- 66,816 counts per minute (mean +/- SD) for eight patients and 119,589 +/- 64,913 counts per minute for 30 controls (P less than 0.05, Student's t test). Treatment with the cyclooxygenase inhibitor indomethacin increased the phytohemagglutin-induced proliferation of the T lymphocytes from five of eight patients, but none of 12 healthy homosexual and heterosexual control subjects. The production of prostaglandin E2 by T lymphocytes from six patients was 16.1 +/- 10.5 pg/5 X 10(6) cells/hr, as contrasted with that of 4.9 +/- 1.3 and 4.3 +/- 2.1 pg/5 X 10(6) cells for four healthy homosexual and six healthy heterosexual control subjects, respectively (P less than 0.01, Student's t test). The production of prostaglandin E2 by the patients' monocytes was normal. Abnormalities of the cyclooxygenase pathway of T lymphocytes of patients with the reactive lymph node syndrome may reflect an immunoregulatory defect, which predisposes to infections and may evolve into the more severe abnormalities of the acquired immune deficiency syndrome.
Recognition of leukotriene B4 by a unique subset of human T-lymphocytes.
Leukotriene (LT) B4, but not 12(S)-LTB4 or LTC4, inhibits the generation of lymphokine-designated leukocyte inhibitory factor by purified human T-lymphocytes. LTB4 coupled to fluorescein-labeled human serum albumin interacts specifically with approximately 11% of the T-lymphocytes as assessed by fluorescence-activated flow cytometry. The LTB4-reactive T-lymphocytes are distributed between the suppressor-cytotoxic (14%) and helper-inducer (8%) subsets, which were identified concurrently by phycoerythrin-labeled monoclonal antibodies to subset-specific antigens. LTB4, but not 12(S)-LTB4 or LTC4, significantly enhances the proliferation of mitogen-stimulated purified suppressor-cytotoxic T-lymphocytes at concentrations of 10(-12)M to 10(-6)M and significantly inhibits the proliferation of mitogen-stimulated purified helper-inducer T-lymphocytes at concentrations of 10(-8)M to 10(-6)M, as assessed by the uptake of [3H]thymidine. The net effect of LTB4 on blood T-lymphocytes is immunosuppression that may be expressed in some human hypersensitivity and inflammatory diseases.
Human T-lymphocyte subset specificity of the regulatory effects of leukotriene B4.
Leukotriene B4, but not (12S)-leukotriene B4, coupled to fluorescein-labeled human serum albumin interacts specifically with human T lymphocytes, as assessed by fluorescence-activated flow cytometry. Approximately 11% of blood T lymphocytes bind the fluorescent conjugate of leukotriene B4. The leukotriene B4-reactive T lymphocytes are distributed between the suppressor-cytotoxic (14%) and helper-inducer (8%) subsets, which were identified concurrently by phycoerythrin-labeled monoclonal antibodies to subset-specific antigens. Leukotriene B4, but not (12S)-leukotriene B4 or leukotriene C4, enhances significantly the proliferation of mitogen-stimulated purified suppressor-cytotoxic T lymphocytes, at concentrations of 10(-12) M to 10(-6) M, and inhibits significantly the proliferation of mitogen-stimulated purified helper-inducer T lymphocytes, at concentrations of 10(-8) M to 10(-6) M, as assessed by the uptake of [3H]thymidine. The net effect of leukotriene B4 on blood T lymphocytes is immunosuppression, which may be expressed in some human hypersensitivity and inflammatory diseases.
Defective polymorphonuclear leukocyte chemotaxis in homosexual men with persistent lymph node syndrome.
Persistent lymph node syndrome, epidemiologically related to acquired immune deficiency syndrome, is characterized by reactive lymphadenopathy and an increased incidence of localized bacterial, viral, and fungal infections. Seven typical patients were found to have a localized infection every 4.5 +/- 2.0 months (mean +/- SD) since onset of adenopathy. Because recurrent bacterial infections may be associated with defective polymorphonuclear leukocyte (PMNL) function, studies of PMNL function in these patients were undertaken. The patients' PMNLs had diminished chemotactic responses to high concentrations of two structurally distinct chemotactic factors, leukotriene B4 and N-formylmethionylleucylphenylalanine. The patients' PMNLs also had deficient degranulating responses to the former but not to the latter. Diminished PMNL function may contribute to the observed increased incidence of localized infections, which are a major source of morbidity, in these patients.
Substance P recognition by a subset of human T lymphocytes.
The interaction of substance P with human blood T-lymphocytes, which stimulates T-lymphocyte proliferation, was quantified by both flow cytometric and direct binding assays. Fluorescence-detection flow cytometry recorded the binding of dichlorotriazinylamino-fluorescein-labeled substance P to 21 +/- 10% (mean +/- SD, n = 6) and 35 +/- 8% (n = 2) of human blood T-lymphocytes before and after stimulation with 10 micrograms/ml of phytohemagglutinin, respectively. The suppressor-cytotoxic (leu 2a) and helper-inducer (leu 3a) subsets identified by phycoerythrin-labeled monoclonal antibodies contained substance P-reactive T-lymphocytes at respective mean frequencies of 10 and 18%. [3H]substance P bound rapidly and reversibly to a mean of 7035 +/- 2850 sites/T-lymphocyte, which exhibited a dissociation constant (KD) of 1.85 +/- 0.70 X 10(-7) M (mean +/- SD, n = 5). [D-Pro2,D-Phe7,D-Trp9]substance P inhibited the binding of dichlorotriazinylamino-fluorescein-labeled substance P and [3H]substance P to T-lymphocytes at concentrations that suppressed the proliferative response to substance P. Substance P, eledoisin, and substance K (alpha-neurokinin), which all share with substance P the carboxy-terminal substituent -Gly-Leu-Met-NH2, were more potent than substance P in inhibiting the binding of [3H]substance P to T-lymphocytes, suggesting the importance of this sequence in the interaction. Purified human blood B-lymphocytes, monocytes, polymorphonuclear leukocytes, and platelets, and cultured Hut 78 cutaneous lymphoma T-cells, Jurkat cells, Molt-4 lymphoblasts, and HL-60 and U-937 monocyte-like cells all showed only minimal specific binding of [3H]substance P. The recognition of substance P by T-lymphocytes provides one mechanism for selective modulation of immunity by sensory nerves.
Stereospecific receptors for substance P on cultured human IM-9 lymphoblasts.
The neuropeptide substance P (SP), which has been demonstrated to bind specifically to human blood T lymphocytes and to stimulate their uptake of [3H]thymidine and [3H]leucine, now is shown to bind stereospecifically to cultured human lymphoblasts of the IM-9 line. The specific binding of [3H]SP by IM-9 lymphoblasts increases linearly with the concentration of IM-9 lymphoblasts, achieves a plateau after approximately 15 to 20 min at 4 degrees C and 4 to 6 min at 37 degrees C, and is rapidly reversible at both 4 degrees C and 37 degrees C. The binding of [3H]SP at steady-state conditions demonstrates a dissociation constant (KD) of 0.65 +/- 0.19 nM (mean +/- SD, n = 5) and 22,641 +/- 6143 receptors per IM-9 lymphoblast. Maximal specific binding of [3H]SP to IM-9 lymphoblasts is observed at pH 7.4 and is dependent on the presence of Mg2+, but not Ca2+, in the medium. The peptide structural determinants of the inhibition of binding of [3H]SP to IM-9 lymphoblasts by substituent peptides and homologs of SP indicate that the receptors recognize predominantly the carboxy-terminal portion of SP. The characteristics of the interaction of SP with IM-9 lymphoblasts suggests a receptor-directed mechanism by which neuropeptides may modulate specifically the contributions of lymphocytes to immunity.
Modulation of immunity and hypersensitivity by sensory neuropeptides.
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